Biology is defined as the study of life / living things. A living thing is defined as anything that converts energy from one form to another, while using that energy to grow, change, and reproduce.
The scientific method is the standard guideline for discovery and experimentation in the sciences (chemistry, physics, biology, etc..) The basic steps are...
The last step (refine and iterate) just means that you do it all over again but make changes based on the things you learned from your experiment. For example, ...
The scientific method revolves around making an observation and coming up with a testable explanation for that observation -- called a hypothesis. If the explanation isn't testable, you can't consider it a hypothesis. For example, a good hypothesis may be that increased sun exposure leads to an increased risk of skin cancer because it's something you can test. A bad explanation may be that exposure to centaurs increase the risk of skin cancer because centaurs don't exist (and as such the hypothesis can't be tested).
Once you have a hypothesis, you design an experiment to test it. In the case of our sun exposure leads to increased risk of skin cancer hypothesis, an experiment may be to expose skin cells to UV rays in amounts equivalent to that given off by the sun and then check to see if those cells have been damaged (compared to a control group of skin cells that you haven't exposed to UV rays).
What makes a good experiment?
Other terminology around the scientific method...
An element is matter that cannot be broken down any further by chemical reaction -- it's a substance made entirely out of one type of atom. Each element/atom has a specific set of properties that defines how it acts/reacts (e.g. weight, colour, how light reflects, etc..).
Examples of elements/atoms:
Examples of non-elements:
The building blocks of atoms are protons, neutrons, and electrons. Protons and neutrons form the nucleus of the atom while electrons jump around outside of the nucleus. Protons and electrons are attracted to each other -- protons are positively charged while electrons are negatively charged. Although, protons and electrons never fully meet (electrons are always buzzing/hovering around the outside of the nucleus where the protons are).
The configuration of an atom (protons/neutrons/electrons) is what allows us to predicate how one element may react to another element. For example, certain elements may attract, repel, bond, swipe electrons, etc..
The number of protons are what defines the type of atom/element. For example, hydrogen has 1 proton, helium as 2, lithium has 3, etc.. The number of neutrons and electrons can change without changing the type of element as long as the number of protons remain the same.
The periodic table below orders elements/atoms by the number of protons (also called the atomic number)...
When atoms bind together, they form a molecule. Each type of molecule has the same configuration of atoms -- same atoms in the same numbers, structured/shaped similarly. For example, a water molecule is made up of 2 hydrogen atoms and 1 oxygen atom binding together in a house-roof shape...
A monomer is a special designation for atoms/molecules that are able to join with other monomers to create even larger molecules. The process of joining is called polymerization and the resulting molecule is called a polymer.
If the monomers that make up a polymer are all the same, the polymer is called a homopolymer. Otherwise, it's called a heteropolymer / copolymer.
For example, the glucose molecule is a monomer. It can combine with other glucose molecules to create the glycogen molecule, which is a polymer / homopolymer. Other examples of polymers (according to Wikipedia): amino acids and nucleotides (DNA).
Polymers are often referred to as macromolecules -- molecules that have a very large number of atoms.
An ion is a charged atom or molecule. A charged atom/molecule just means that it has an unequal number of protons and electrons:
Ions are always trying to lose their charge and become neutral, either by giving up an electrons or pulling in an electrons such that the the number of protons and electrons become equal. As such, ions will attract towards oppositely charged ions and repel from similarly charged ions:
pH stands for potential of hydrogen and it's the measure of positively charged hydrogen ions in a solution. The more...
pH is scaled logarithmically from 1 to 14. Each notch on the scale moves the acidity/basicity by a factory of 10. Going...
For example, going from 7 to 4 increases acidity by 1000x times / decreases basicity by 1000x.
The closer to...
Carbohydrates (also called saccharides) are molecules that consist of a mix of carbon, hydrogen, and oxygen atoms. In biological systems, carbohydrates are often associated with...
The term monosaccharide is just means a carbohydrate that's a monomer (e.g. glucose). Similarly, the term polysaccharide means a carbohydrate built from other monosaccharides (e.g. glycogen is made of chained glucose).
Proteins are molecules that consist of monomers called amino acids. The amino acids get chained together into a polymer called a polypeptide chain, and one or more polypeptide chains fold to a 3D structure and combine to become a protein. The 3D structure / shape of the protein (how its folded) is what gives it its abilities.
In biological systems, proteins are often associated with that facilitating some biological function. For example, the protein protease is responsible for breaking down food.
The basic structure of an amino acid is as follows. The R is a placeholder that, when set, defines what type of amino acid it is...
Lipids are molecules that are somewhat not water soluble -- meaning that they have parts that resist water but maybe also parts that are attracted to water. In biological systems, lipids are often associated with...
Nucleic Acid is a molecule (heteropolymer) often associated with information storage. It's built up from other molecules called {bm} nucleotides (monomers). It's called nucleic acid because it's in the nucleus of a cell and it has some acidic properties to it.
Deoxyribonucleic acid (DNA) is the most common form of nucleic acid. DNA is a molecule that contains the instructions needed for the growth/functioning/maintenance of an organism. Depending on the type of organism, DNA is located either in the cell’s nucleus (for eukaryotic organisms -- animals and plants) or the cell’s cytoplasm (for prokaryotic organisms -- single-celled organism).
Ribonucleic acid (RNA) is another common form of nucleic acid. RNA is a molecule used as a transferring mechanism for copying over information from DNA to other cellular machinery. It's also used as information storage for (some?) viruses.
The monomers that make up nucleic acid molecule are called nucleotides, and the order they appear in defines the genetic information/instructions.
There are 5 different nucleotides:
The order the appear in defines the genetic information/instructions of that organism. Because they are the unit by which genetic information is encoded, each nucleotide is also called a base. For example, a string/sequence of DNA bases: ATATTTTCGATATCCACCA.
The two nucleotides/molecules that make up a connection are called a base pair. The rules to base pairs are…
Water is essential to life -- it has unique properties that almost all biological processes depend on.
Recall that...
Oxygen atoms are extremely electronegative, meaning that oxygen has the propensity to pull the buzzing/hopping electrons more around itself than the atoms it's bound to. As such, in a water molecule, the electrons will spend more time solely around the oxygen atom than they do the hydrogen atom or a position that binds the hydrogen and oxygen together. This is what gives the oxygen atom in a water molecule a weakly negative charge (as indicated by δ-) while the hydrogen atoms have a weakly positive charge (as indicated by δ+). These types of charged molecules are called polar molecules.
This weakly negative / weakly positive charge is what gives water several of the unique properties that biological properties depend on. Water molecules have a tendency to gravitate towards each other because the weakly negative oxygen atoms and the weakly positive hydrogen atoms of different water molecules attract. This attraction is called a hydrogen bond. Hydrogen bonds are weaker than covalent bonds in that the bonds aren't really solid -- water molecules can easily break off and go past each other.
The weak attraction between water molecules is also what makes water a solvent. So long as they're polar molecules, other molecules can travel inside of water using the same attraction from weakly negative / weakly positive charges -- they gravitate and float around water molecules just as other water molecules do. For example, the cytoplasm of a cell is a solvent (mostly water). It works because other molecules in the cytoplasm (e.g. cellular machinery) can float around / travel around using the weakly negative / weakly positive charges.
Water is called a universal solvent because it can dissolve more molecules than other other liquid. Note that the term universal doesn't mean that it can dissolve everything, just that it can dissolve more things than the others.
The properties that make water conducive for biological processes to operate:
Other terminology related to water:
Cells are the basic unit of living things / the building blocks of life. They're tiny structures that encapsulate information and machinery that allows them to replicate/reproduce and perform other important functions (e.g. appendages to move around).
There are 2 types of cells: eukaryotic and prokaryotic. There main differences between them are that...
Other differences between eukaryotes and prokaryotes ...
| Eukaryotes | Prokaryotes | |
|---|---|---|
| Size | 10 to 100 micrometers (μm) | 0.1 to 5 micrometers (μm) |
| Complexity | More complex | More simple |
| Sub-compartments (organelles) | Yes | No |
| DNA layout | Multiple stands | Single circular strand |
| Single-cell organisms | Yes (e.g. amoeba) | Yes (e.g. bacteria and archaea) |
| Multi-cell organisms | Yes (e.g. animals and fungus) | No |
Different cell species vary in features. The subsections below detail common cell features (not exhaustive).
Some features are only present in certain cell speicies (e.g. only some cells have a flagellum tail) while other features are present in all cells but in different amounts (e.g. every cell has cytosol but larger cells have more cytosol).
The cytoplasm (both eukaryotic and prokaryotic) is the insides/guts of a cell. Cytosol refers to just the fluid, while cytoplasm refers to fluid as well as everything else inside the cell.
The plasma membrane (present in both eukaryotic and prokaryotic cells) is the thing encapsulating the cytoplasm. It's what keeps the guys of the cell inside and controls the movement of substances coming into / going out of the cytoplasm.
Every cell has a membrane encapsulating its cytoplasm. Membranes in general follow the fluid mosaic model.
The term membrane can refer to either the plasma membrane or the membrane of a eukaryotic cell's organelle. How you should interpret it depends on the context in which its used.
The cell wall (present in both eukaryotic and prokaryotic cells) is a stiff layer around the membrane meant for protection. Not all cells have a cell wall -- for example, animal cells don't but plant cells do. Technically, the cell wall (if it exists) isn't considered to be part of the cell. The membrane and everything in it is.
The material states that cell walls...
Almost all prokaryotes have cell walls. Only some eukaryotes have cell walls (e.g. fungi and plants). The material says that cell walls for most bacteria are made up of a molecule called peptidoglycan, but it can be different for other cells. For example, this link says that plant cells have cell walls made up of cellulose.
The Capsule (present in prokaryotic cell only) is the outermost layer of some types of cells (typically bacteria cells). Capsules are made up of carbohydrates and there mainly to help the cell stick itself to the environment.
Ribosome (present in both eukaryotic and prokaryotic cells) are tiny molecular machines inside the cytoplasm that take in mRNA molecules (portions of DNA that have been written out) and produce proteins. Ribosomes themselves are structures made of proteins and RNA.
Ribosomes can either be floating around in the cytoplasm (called free ribosome) or be embedded in the membrane of endoplasmic reticulum.
Some cells have appendages that help them move (or stay put). There are different types of appendages...